IntroductionAquatic organisms parti

Introduction
Aquatic organisms participate in various processes leading to water purification.
Not onlymicroorganisms, but also invertebrates [1, 2] and many other groups of organisms are involved [3-8], which was discussed and analyzed in [9-12].
This paper generalizes and systematizes the basics of the theory of the multifunctional role thatthe biota plays in the self-purification [1–3, 7, 13, 14, 15] and ecological remediation [11] of aquatic ecosystems using the results of previous analyses [3–12, 15, 16, 17].
When using the expression 'water self-purification', we mean a system of natural processes that lead to improving water quality as a result of the interplay of natural factors without any man-made attempts to treat or purify water.
The analysis is made at the qualitative level. Some details of the methods, experiment and additional references were given in [7, 15].
This paper is based on the presentations that the author made at the recent conference 'Aquatic Ecosystems and Organisms-6' (the 6th international conference that was run in Moscow in 2004, at Moscow University; organized by the Department of Hydrobiology), and recent American Society of Limnology and Oceanography (ASLO)
Meetings.